1. Field of Invention
This invention relates to the method and apparatus for wire-bonding an insulated and coated wire, and in particular to the method and apparatus for wire-bonding an electrically conductive wire of an insulated and coated wire, in the wiring of a semiconductor device or printed circuit board where an insulated and coated wire is used, to an electrically conductive electrode.
2. Description of the Prior Art
Conventionally, when an insulated and coated wire is connected to an electrode in a circuit board of a semiconductor device, the electrode is beforehand plated with solder metal as described in `Welding Technology` (March 1983, PP. 23-27), and an insulated and coated wire is placed on the electrode. Then a heated capillary is used to melt the solder on the electrode. With this melting, the wire is connected to the electrode by the so-called reflow soldering method. If in this case the insulated and coated wire uses polyurethane as a material of the insulated coating, the solder metal on the electrode is transferred to the electrically conductive wire material and the connection is readily achieved because the polyurethane melts at about 300.degree. C.
In the case of connecting an insulated and coated wire to an electrically conductive electrode which is made of gold, silver, aluminum, copper, etc. or an electrode which consist of a plating of an alumina ceramics, a tungsten layer, then a nickel layer on the tungsten layer, and further gold, aluminum, etc. on the nickel layer as in the internal wiring of a semi-conductor device, the temperature to which a capillary is heated is further raised to melt the metal on the top surface of the electrode and the connection between an insulated and coated wire and electrode can be carried out in the same manner.
In the prior art as described above in which an insulated and coated wire is connected to an electrically conductive electrode, a portion of the insulated coating which does not come in direct contact with the capillary which is heated to a high temperature and is not involved in the connection is melted to expose an excessive length of the electrically conductive wire material. This exposed wire material may cause shortcircuiting by its contact with another exposed wire material or a leakage current by its contact with the surface of an electrode, and the molten insulated coating may be attached to an electrically conductive electrode and obstruct the connection between the electrode and the insulated and coated wire. Consideration has not been given in the prior art to the problems of the inconveniences due to the above mentioned troubles.